1. Field of the Art
The present invention relates to a resist underlayer coating forming composition used for a mask blank that has a resist underlayer coating under a chemically-amplified type resist coating. Specifically, the present invention relates to a resist underlayer coating forming composition comprising a polymer compound having a halogen atom-containing repeating structural unit and a solvent. Further, the present invention relates to a mask blank in which a resist underlayer coating composed of the resist underlayer coating forming composition is formed, and a mask prepared by using the mask blank.
2. Description of the Related Art
A photomask (reticle) used in micro-processing technique of semiconductor devices is produced by patterning an opaque film formed on a transparent substrate. The patterning of the opaque film is carried out by for example etching by use of a resist pattern as a mask. The resist pattern is formed by for example electron beam lithography process and the like.
In recent years, in the mask production field, it is considered to make an accelerating voltage of electron beam used in the electron lithography process 50 eV or more. This is because it is required to lower forward scattering of electron beam passing electron beam resist and to improve beam convergence of the electron beam so that finer resist pattern would be resolved. When the accelerating voltage of electron beam is low, forward scattering occurs on the surface of the resist or in the resist, and the forward scattering deteriorates the resolving property of the resist. However, when an accelerating voltage of electron beam of 50 eV or more is applied, forward scattering is reduced inversely proportional to the accelerating voltage, and energy provided to the resist by the forward scattering is reduced, and thus the resist occur shortage of sensitivity in case where for example an electron beam resist for an accelerating voltage of 10 to 20 eV, or the like is used, and therefore fall of throughput occurs.
In case where is used a chemically-amplified type resist coating in the mask production field, it is known that for example when the vicinity of the surface of a base coating is in state of a relatively low film density or in a rough state, a problem that the chemically-amplified type resist coating is deactivated may occur. Concretely, an acid-catalyzed reaction during patterning is inhibited in the interface between an anti-reflective coating of chromium oxide that becomes a base coating and a resist coating, and thereby the resolving property is often deteriorated in the bottom part of the resist pattern. In this case, shape defects such as a shape defect in the bottom part in for example a chemically-amplified type resist coating of positive type, or a crack in negative type occur.
It is assumed that this is responsible for an apparent lowering of the sensitivity of chemically-amplified type resist coating in the interface with the base coating (deactivation of resist coating) for example by suppression (quench) of the acid generated in the resist coating by exposure to light with a base component on the chromium oxide surface, or by diffusion of the acid to the chromium oxide side.
As methods for resolving the problem of the above-mentioned shape defects, it is reported to introduce an inorganic coating of silicide materials or an organic anti-reflective coating as a base coating (anti-deactivation coating) (see, for example Patent Document 1).
On the other hand, Patent Document 2 discloses an anti-reflective coating forming composition comprising a polymer material containing halogen atom for forming an anti-reflective coating that strongly absorbs a light at wavelength 157 nm.    Patent Document 1: JP-A-2003-107675 (2003)    Patent Document 2: WO 03/071357 pamphlet